Launch of a Black Brant VC sounding rocket from White Sands,
New Mexico carrying an X-ray astronomy payload. While scanning across the Coma
cluster of galaxies, this detected an intense soft and steep-spectrum X-ray
source that was later (12 Jun 1975) redetected by the low-energy X-ray
telescope on SAS-3. The source was
soon identified with the hot white dwarf HZ 43, and, after competing
theories for the X-ray emission mechanism were considered and rejected, this
is now recognized as being the first detection of photospheric X-ray
emission from a (single) white dwarf. See Margon et al. (ApJ, 203, L25,
1976) and Hearn et al. (ApJ, 203, L21, 1976) for more details concerning these
observations. In the interval between these two observations, the white dwarf
in the Sirius system (Sirius B) was observed and detected by the soft
X-ray detector on the ANS satellite, thereby
becoming the second white dwarf detected as a photospheric X-ray source:
see Mewe et al. (Nature, 256, 711, 1975) for the discovery report.

5 Apr 1974

First X-ray detection of Alpha Aurigae or Capella, a nearby pair
of cool giant stars in a binary system with a 104-day orbital period,
by a proportional counter onboard a sounding rocket. See Catura et al.
1975, ApJ, 196, L47 for more details about this discovery, which was the
first detection of X-rays from the coronae of normal stars
(apart from the Sun, of
course, which was first detected in 1948 as an X-ray emitter): until this
date, all discrete extrasolar X-ray sources had either been identified
with unusual objects such as (i) binary systems containing accreting black
holes, neutron stars or white dwarfs, (ii) supernova remants, and
(iii) external galaxies and quasars, or had not had
reliable counterpart identifications at other wavelengths.

8 Jun 1973

A power failure on the Second
Small Astronomical Satellite (SAS 2) terminates its collection of
data. The gamma-ray (20 MeV to 1 GeV) instrument on this satellite
detected the diffuse gamma-ray background as well as a handful of
spatially compact discrete gamma-ray sources.

Formation of the European
Space Agency (ESA), `Europes's gateway to space'. This multinational
entity superceded the European Launcher Development Organization (ELDO) and
the European Space Research Organization (ESRO). Its mission is `to shape
the development of Europe's space capability and ensure that investment in
space continues to deliver benefits to the people of Europe'.

Launch of the Copernicus satellite,
also known as the Third Orbiting Astronomical Observatory 3 (OAO 3).

14 May 1972 at 03:46 UT

First detection of a gamma-ray burst (GRB) at X-ray energies
in the 7-100 keV energy range,
simultaneously with its detection in hard X-rays and gamma-rays, by the UCSD
Cosmic X-ray Telescope on the OSO-7
satellite. The fluence or time-integrated flux
of this strong GRB was ~ 5 x 10-4 erg cm-2.

First secure identification of the compact object in an X-ray binary
system as an infinitely collapsed star or black hole. The optical
companion (HDE 226868) to the X-ray
source Cyg X-1 had been identified in 1971, and subsequent radial-velocity
studies of this star, together with an assumption for its likely mass, implied
a mass for the compact object which excluded other possibilities such as a
neutron star. (See Webster & Murdin 1972, Nature,
235, 37 and Bolton 1972, Nature, 235, 271 for more details). As an
interesting aside, the term "black hole" for an infinitely collapsed object
had been coined only one year previous to this by John Wheeler.

1972

First identification of a cataclysmic variable(a close binary system
with a white dwarf star accreting matter from its cool dwarf star
companion), EX Hydrae, with an X-ray source that had been
previously detected by the Uhuru satellite: see Warner 1972, MNRAS, 158,
425, for more details. (It was subsequently realized that the Uhuru X-ray
source, due to the detector's low spatial resolution, actually was
probably a composite source, with similar amounts of X-ray emission from
EX Hya and a cluster of galaxies which lies only 20 arcminutes away).

At 18:28 GMT, Soyuz 11 undocks from the Salyut 1 space station.
At 23:17, Soyuz 11 landed. When the capsule was opened, all three
cosmonauts (Georgi Dobrovolsky, Vladislav Volkov, and Viktor Patsayev)
were found dead. Further investigation revealed that a valve had been
jerked open by the separation of the orbital and landing modules,
bleeding out the atmosphere of the capsule into space.

Launch of an Aerobee-350 sounding rocket from Wallops Island,
Virginia carrying X-ray polarimeters, which obtained the first
significant detection of linear polarization in the X-ray band of any
extrasolar object, namely the Crab supernova remnant. The amount
and position angle of this polarized emission agreed well with that found in
optical emission from the SNR, and `provides conclusive evidence for
[it being produced by] the synchrotron emission mechanism'. See Novick
et al. (ApJ, 174, L1, 1972) for more details.

21 Dec 1970 - 20 Jan 1971

A series of observations of the Magellanic Clouds by the Uhuru X-ray
observatory detected
diffuse emission as well as three discrete sources in the Large Magellanic
Cloud (extending previous rocket observations which had found two sources),
dubbed LMC X-1, LMC X-2, and LMC X-3, and one highly variable source in
the Small Magellanic Cloud, dubbed SMC X-1. The latter source varied on
a time scale of hours, implying a size no bigger than the solar system; this
was the first detection of `an X-ray source of stellar dimensions in an
external galaxy': see Leong et al., ApJ, 170, L67, 1971 for more
details.

15 Dec 1970

Venera 7 lands on Venus and begins transmitting
data, making it the first lander to successfully function after a soft
landing on another planet.

12 Dec 1970

Launch of Uhuru
(SAS 1), the first earth-orbiting mission entirely dedicated to
X-ray astronomy. The satellite's name means "Freedom" in
Swahili.

24 Sep 1970 at 12:54 UT

Launch of a Thor missile from Johnston Atoll that carried three
proportional counters and 13 scintillation counterssensitive to 1.5 to 12 (?)
keV and 5 to 75 keV X-rays, respectively. This experiment detected
a very hard and extended towards the Small Magellanic Cloud, the first
X-ray detection of the SMC, re-detected the Large Magellanic Cloud
(detected for the first time in a similar flight on 29 Oct 1968) with
a strong suggestion that its X-ray emission was due to two separate spatial
sources: see Price et al., ApJ, 168, L7, 1971 for more details.

Launch of a Terrier-Sandhawk rocket from Kauai, Hawaii that carried
a 640 square cm proportional counter sensitive to 0.2 to 12 keV X-rays. This
experiment detected a score or so of discrete sources, including the Puppis
and Vela SNRs, and the peculiar star Eta Carinae. Eta Carinae,
arguably the most massive star in the Milky Way Galaxy, has been extensively
studied for over 150 years since it prolonged outburst in the 1830's and
1840's when it was the second brightest star in the sky, but much still remains
to be understood about it. Its bright and hard X-ray emission has likewise been
extensively studied for the more than 30 years since this rocket flight,
and modern studies suggest that it is mostly due to the winds from
the observed star and a fainter secondary star colliding and being shock-heated
to high temperatures (>= 50 million K).

24 Apr 1970

First detection of Quasi-Periodic Oscillations (QPOs) in the X-ray
emission from an X-ray binary system, in an observation of Sco X-1 by
proportional counters flown on an Aerobee rocket: see Angel et al. (ApJ, 169,
L57, 1971) for more details. This, and a subsequent Hakucho observation of
QPOs in the Rapid Burster (Tawara et al. (Nature, 299, 38, 1982), ushered
in a `Golden Age' of QPOs brought about by the superior timing capabilities
in this regard of the EXOSAT Observatory: see Lewin at al. (Space Sci Revs,
46, 273, 1988) for an EXOSAT-era review of the QPO phenomenon.

8 Apr 1970

Co-launch of the Vela
6A and 6B satellites, the final pair of Vela satellites that were launched
in order to monitor compliance with the Limited Test Ban Treaty of 1963.
Together with the Vela 5A and Vela 5B satellites,
these satellites are often credited with the first discovery of the
events called gamma-ray bursts (GRBs) although it was later realized that the
Vela
4A and Vela 4B satellites had actually earlier detected at least one GRB
in 1967.